How to Maintain Image Aspect Ratio When Cropping Images in PHP?

Image Cropping in PHP

When cropping images in PHP, you may encounter problems, especially when dealing with large images. One workaround is to "shrink the image".

In the given example code, the image is cropped to a fixed size (200x150), which may not fit larger images. To obtain consistent image dimensions before cropping, it is recommended to use the imagecopyresampled() function.

The following formula can be used to generate thumbnails:

$image = imagecreatefromjpeg($_GET['src']);
$filename = 'images/cropped_whatever.jpg';

$thumb_width = 200;
$thumb_height = 150;

$width = imagesx($image);
$height = imagesy($image);

$original_aspect = $width / $height;
$thumb_aspect = $thumb_width / $thumb_height;

if ( $original_aspect >= $thumb_aspect )
{
    // 图像更宽（纵横比意义上）
    $new_height = $thumb_height;
    $new_width = $width / ($height / $thumb_height);
}
else
{
    // 缩略图更宽
    $new_width = $thumb_width;
    $new_height = $height / ($width / $thumb_width);
}

$thumb = imagecreatetruecolor( $thumb_width, $thumb_height );

// 调整大小并裁剪
imagecopyresampled($thumb,
    $image,
    0 - ($new_width - $thumb_width) / 2, // 水平居中图像
    0 - ($new_height - $thumb_height) / 2, // 垂直居中图像
    0, 0,
    $new_width, $new_height,
    $width, $height);
imagejpeg($thumb, $filename, 80);

This code takes the image aspect ratio into account, ensuring that the resized image has the same aspect ratio as the thumbnail size, thus preventing distortion . After resizing and cropping, it will produce a consistently sized image regardless of the original image size.

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